Agitation and mixing of chemical and biological fluids is accomplished with precision in laboratory and production facilities with shakers, examples which are shown in U.S. Pat. Nos. 3,002,895, 3,430,926, 3,601,372 and 3,830,474 sold commercially under the name Gyrotory.RTM.by New Brunswick Scientific Co., Inc. of Edison, N.J. Such shakers are adapted to carry a variety of containers such as glass flasks of the Erlenmeyer type and test tubes, frequently in quantity, on a platform which is motor-driven through a drive geometry capable of high speed and high eccentric forces to obtain the desired mixing or agitation over a specified period, which may range from minutes to days.
The flasks are commonly held on the shaker or moving platform by a multi-leaved or multi-splined spring clip which has outwardly flared upper edges to allow insertion and removal of the flask. The spring tension of the clip, which theoretically can be sufficiently high to hold the flask during shaking, as a practical matter must be sufficiently low to permit insertion and removal of the flask. As the design envelope for shaker speeds and eccentric forces increase, this practical limitation on spring tension has begun to manifest itself in the form of flasks vibrating in their spring clips until some failure is reached. Failure may run from non-conformity with shaking requirements (uniformity, no air bubbles, etc.) to catastrophic breakage of the flasks. In cases of microbial cultures, uniform cell growth may depend on flask stability during agitation. Flasks which are not firmly held may have significantly changed agitation patterns and unacceptable oxygen transfer rates. In addition, flasks which are not firmly held may be agitated at differing rates which affects accurate repeatability of agitation runs.
Prior devices for releasably securing flasks include a coil spring with a closure for opening and closing the coil spring around the splines of the clip. Such devices are relatively expensive to make, hard to clean (a particular disadvantage in sterile or controlled environments) and difficult to manipulate in close quarters resulting in improperly secured flasks.